The recent emergence of 3rd Generation and higher mobile wireless communications systems creates a need for mobile communications handsets capable of accessing multiple communications systems, for example GSM and W-CDMA communications systems serving a common geographical area.
The full exploitation of the services of multiple communication systems requires that multi-mode wireless mobile communications devices operate simultaneously on more than one communication system and transition efficiently therebetween without significant performance degradation.
Multi-mode and multi-band wireless communications handsets are known, but presently these known devices are incapable of accessing more than one communication system simultaneously. In homogeneous communications systems with sufficient frequency separation, for example, Time Division Multiple Access (TDMA) systems, multi-band communication handsets are capable of efficiently assessing handoff candidates on another frequency. The continuous receive and transmit nature of CDMA communications, however, leaves no time for monitoring other communication systems as required for multi-mode operation, for example for assessing hand-off candidates.
It is known to compress the transmission of downlink and uplink information in continuous receive and transmit communications systems to create time for monitoring other communication systems. During compression, more data is transmitted over shorter time intervals to avoid a reduction in the data rate. Transmission compression however requires more power, resulting in increased burdens on system capacity.
The various aspects, features and advantages of the present invention will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description of the Invention with the accompanying drawings described below.